A liquid crystal display device utilizes optical anisotropy, dielectric anisotropy or the like of liquid crystal molecules in a liquid crystal composition. A classification based on an operating mode for liquid crystal molecules includes a phase change (PC) mode, a twisted nematic (TN) mode, a super twisted nematic (STN) mode, a bistable twisted nematic (BTN) mode, an electrically controlled birefringence (ECB) mode, an optically compensated bend (OCB) mode, an in-plane switching (IPS) mode, a fringe field switching (FFS) mode, a vertical alignment (VA) mode and so forth.
The liquid crystal display device having a mode in combination of a polymer with a liquid crystal composition is known. The mode is a polymer sustained alignment (PSA) mode or a polymer stabilized (PS) mode, for example. In the liquid crystal display device having the mode, the liquid crystal composition to which the polymerizable compound is added is injected into the display device. The polymerizable compound is polymerized by irradiating the compound with ultraviolet light in a state of applying voltage between electrodes to form the polymer in the liquid crystal composition. According to the method, the liquid crystal display device is obtained in which a response time is shortened and image persistence is improved.
The above method can be applied to the liquid crystal display devices having various operating modes, and the modes such as a PS-TN mode, a PS-IPS mode, a PS-FFS mode, a PSA-VA mode and a PSA-OCB are known. The polymerizable compound used in the device having such a mode is considered to have a high capability for aligning liquid crystal molecules, but solubility thereof in the liquid crystal composition is far from high. An attempt for improving the solubility in the liquid crystal composition has been made so far, but if the solubility in the liquid crystal composition is improved, polymerizability tends to decrease. Therefore, desire has been expressed for development of the polymerizable compound having a suitable balance between the solubility and the polymerizability.